<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1, user-scalable=no">
    <meta http-equiv="X-UA-Compatible" content="ie=edge,chrome=1">
    <meta name="author" content="贾文清">
    <title></title>
    <style>
        body {
            margin: 0;
        }

        ul {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        main {
            width: 600px;
            height: 650px;
            margin: 0 auto;
            border: 1px solid red;
        }

        .first {
            width: 600px;
            height: 400px;
            position: relative;
            padding-top: 10px;
            display: flex;
            justify-content: space-around;
        }

        .right {
            width: 350px;
            height: 350px;
        }

        .right img {
            width: 350px;
            height: 350px;
            border-radius: 5px;
        }

        .left {
            width: 230px;
            height: 350px;
        }

        .left ul li {
            width: 100px;
            height: 100px;
            margin: 0 auto;
            margin-top: 10px;
        }

        .left img {
            width: 100px;
            height: 100px;
            border-radius: 5px;
        }

        .second {
            width: 600px;
            height: 250px;
        }

        .second ul {
            display: flex;
            justify-content: space-around;
        }

        .second ul li {
            width: 100px;
            height: 100px;
            margin: 0 auto;
            margin-top: 10px;
        }

        .second ul img {
            width: 100px;
            height: 100px;
            border-radius: 5px;
        }
    </style>
</head>

<body>
    <main>
        <section class="first">
            <div class="right">
                <img src="./img/big_1.jpg" alt="">
            </div>
            <div class="left">
               <ul>
                <li><img src="./img/big_1.jpg" alt=""></li>
                <li><img src="./img/big_2.jpg" alt=""></li>
                <li><img src="./img/big_3.jpg" alt=""></li>
               </ul>
            </div>
        </section>
        <section class="second">
            <ul>
                <li><img src="./img/big_4.jpg" alt=""></li>
                <li><img src="./img/big_5.jpg" alt=""></li>
                <li><img src="./img/big_6.jpg" alt=""></li>
                <li><img src="./img/big_7.jpg" alt=""></li>
            </ul>
            <ul>
                <li><img src="./img/big_8.jpg" alt=""></li>
                <li><img src="./img/big_9.jpg" alt=""></li>
                <li><img src="./img/big_10.jpg" alt=""></li>
                <li><img src="./img/big_11.jpg" alt=""></li>
            </ul>
        </section>
    </main>

</body>

</html>
<script>
    var right = document.querySelector('.right img');
    var allLi = document.querySelectorAll('li');
    for (var i = 0; i < allLi.length; i++) {
         allLi[i].index = i+1
         allLi[i].onmouseover = function () {
           right.src = './img/big_'+this.index+'.jpg';

        }
    }

</script>